Metal-dielectric Structures Research Articles

Studying C-V characteristics of MIS structures with ALD Al-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=- on n- and p-CdHgTe stabilized with ultra-thin native oxide

Capacitance--voltage characteristics of metal dielectric semiconductor structures with atomic layer deposition Al2O3 on n- and p-Cd0.22Hg0.78Te (with and without a surface graded-gap layer) preliminary oxidized in oxygen glow discharge plasma (with the resulting oxide thickness of 2 nm) have been studied. The obtained structures reveal the positive fixed charge with a density of ~(1-6)·1011 cm-2. The ratio between a slow surface states density and a surface band gap width is almost independent on graded-gap layer presence, with the value of ~(4-8)·1011 cm-2·eV-1. The proposed passivation approach provides near-ideal low-frequency capacitance-voltages characterized by weak influence of fast surface states. Films of CdHgTe grown without the graded-gap surface layer are proved to be much more sensitive to the process of oxidation in glow discharge plasma. Keywords: mercury cadmium telluride, film, surface states, plasma.

Анализ динамики затухания люминесценции в металл-диэлектрических фотонных структурах с органическими слоями

Metal-dielectric photonic structures with organic materials 4,4-bis(N-carbazolyl)-1,1-biphenyl and 4,4′-bis[4-(di-ptolylamino)styryl] biphenyl) as light emitting layers were investigated. The formation of the polaritonic modes in the investigated structures was experimentally demonstrated and a correlation between theoretical and experimental dispersion was shown. Was shown, that increase in interaction between organic exciton and optical mode leads to a significant decrease in the lower polariton emission bandwidth.

Расчет напряженности электрического поля в интерференционных покрытиях

A technique for calculating the electric field in interference coatings is described. The technique is used to find areas in the coating structure with electric field minima. Thin absorbing metal films are introduced into these areas during design. The results of calculating the transmission spectra of narrow-band interference filters with absorbing metal films are presented. It is shown that such metal-dielectric thin-film structures block radiation in the long-wavelength region of the spectrum.

Calculation of the electric field in interference coatings

A technique for calculating the electric field in interference coatings is described. The technique is used to find areas in the coating structure with electric field minima. Thin absorbing metal films are introduced into these areas during design. The results of calculating the transmission spectra of narrow-band interference filters with absorbing metal films are presented. It is shown that such metal-dielectric thin-film structures block radiation in the long-wavelength region of the spectrum. Keywords: electromagnetic field amplitude, narrow-band interference filters, spectra, films, absorption, transmission.

Influence of the radius of a perfectly conducting cylinder on the radiation pattern of a patch antenna

In this paper, we consider the change in the directional pattern of a microstrip patch antenna located on a perfectly conducting plane and a cylinder covered with a dielectric layer. The mathematical apparatus of the Green’s tensor functions for flat and cylindrical layered metaldielectric structures is used to calculate field characteristics. The obtained results are of special interest in the design of conformal single radiators and antenna arrays located on curved surfaces that can be approximated by a cylinder, for example, the fuselage of small-sized aircraft or supports for the installation of antenna systems. It is demonstrated that the curvature of the base surface for a single element has little effect on the radiation pattern within the width of the main lobe; nevertheless, the increase in the radius of the used cylinder influences the level of the back lobe significantly.

The multi-energetic Au ion implantation of graphene oxide and polymers

The electric properties of polymers are increasingly important in a wide range of applications such as sensors, energy storages, microelectronics, and filtration membranes among others. In this work, the effect of multi-energetic Au ion implantation on the graphene oxide (GO), polyimide (PI), polyethylene terephthalate (PET) and polylactide (PLLA) elemental, chemical, structural end electric properties is presented with potential application in 3D metal-dielectric structure synthetization. The three energies, 3.2, 1.6, 0.8 MeV of Au ions with fluence 3.75×1014 cm-2 were used in ascending or descending order to create two sample sets, which were subsequently analysed by RBS, ERDA, EDS and AFM. RBS analysis was used for Au-depth profile characterization in the implanted samples, the profiles agree reasonably with those simulated by SRIM code. Electrical properties were investigated by standard two-point technique with respect to the used parameters of the ion irradiation. The sheet resistance decreases after ion irradiation and it is evident that the ascending order of ion implantation energies has more significant effect on the conductivity enhancement compare to the descending one.

The influence of the PZT buffer layer on electrophysical properties OF MDM structures with the BST film

Films of the composition Ba0.8Sr0.2TiO3 (BST) were synthesized by the method of high-frequency (HF) sputtering on the buffer layer of a ferroelectric film of the composition PbZrxTi1-xO3 (PZT). Comparative results of electrophysical properties of three different metal--dielectric--metal (MDM)-structures are presented: Pt/BST/Ni, Pt/PZT/Ni, and Pt/PZT-BST/Ni. Keywords: metal--dielectric--metal structures, ferroelectric films of composition Ba0.8Sr0.2TiO3, a buffer layer, electrophysical properties.

The influence of the PZT buffer layer on electrophysical properties of MDM structures with the BST film

Films of the composition Ba0.8Sr0.2TiO3 (BST) were synthesized by the method of high-frequency (HF) sputtering on the buffer layer of a ferroelectric film of the composition PbZrxTi1-xO3 (PZT). Comparative results of electrophysical properties of three different metal--dielectric--metal (MDM)-structures are presented: Pt/BST/Ni, Pt/PZT/Ni, and Pt/PZT-BST/Ni. Keywords: metal--dielectric--metal structures, ferroelectric films of composition Ba0.8Sr0.2TiO3, a buffer layer, electrophysical properties.

Investigation of the dynamics of heating metal-dielectric structures with nanometer conductive film under the influence of microwave fields

The paper presents the results of experimental studies and analysis of the dynamics of heating of metal-dielectric structures (MDS) with aluminum conducting films on glass or sitall substrates when exposed to powerful microwave fields, as well as when exposed to direct and alternating currents.

High Q-factor plasmonic filter based on MIM structures and its application in the design of a dual band demultiplexer for optical communication wavelengths

One of the key components in optical integrated circuits is bandpass filters. In this article, a scheme of plasmonic filters consisting of a nanodisk cavity coupled with two T -shaped metal–insulator–metal (MIM) waveguides is presented. The nanodisk cavity is in a square or rectangular shape. The effects of the geometrical parameters variations on the transmission spectrum are investigated. The results of the numerical simulation analysis indicate that the perfect transmission peak can be achieved by optimizing the structure parameters. Hence, the appropriate dimensions of this structure for operating in the optical communication wavelength range (from O to L bands) are obtained. Also, the proposed filter exhibits the transmission peak of 0.99 and the high quality factors ( Q -factors) of 91 and 109.25 at the wavelengths of 1550 nm and 1310 nm, respectively. In addition, a design of two-channel demultiplexer is presented, in which the waveguides are connected by T or Y junctions. The results show that the proposed structure exhibits the transmission peaks of 0.8 and 0.67 and the Q -factors of 65 and 103.3 at the resonance wavelengths of 1310 nm and 1550 nm, respectively.

Electromagnetically induced transparency-based metal dielectric metamaterial and its terahertz sensing application.

In this paper, electromagnetically induced transparency has been reported in the metal-dielectric structure that provides the platform for high-quality factor Fano resonance in the terahertz region. The electric dipole in the metal ring provides a bright mode, while the electric and magnetic dipoles formed in the dielectric offer bright and dark modes, respectively. Two resonance dips have been obtained with a high-quality factor of 89.5 and 23 leads to a high figure of merit of sensor equal to 6 and 4 for the first and second resonance dips, respectively, which is useful for the design and development of metamaterial-based sensing devices and biosensors.

Fabrication of metal-dielectric nanoparticles from a bi-layer gold-silicon film by femtosecond laser-induced dewetting

Today the world demand for the creation of highly efficient nanoscale white light sources is growing. It happens because energy-efficient information and communication systems are being developed, in which optical signals are replacing electrical signals. For the fabrication of such devices, creating efficient nanoscale white light sources with high efficiency is very acute. Such structures obtained by current methods have a common disadvantages: a small spectral width and low efficiency. Here we demonstrate the development of metal-dielectric structures exploiting the single-step and lithography-free laser-induced dewetting of bi-layer gold silicon films and study their broadband photoluminescence.

Sub-Diffraction-Limit Imaging System with two Interfacing Hyperbolic Metamaterials

It is demonstrated that a system of two interfacing hyperbolic metamaterials may be used for direct subwavelength imaging in the visible range. The proposed configuration consists of two anisotropic photonic crystals: a multilayered metal-dielectric structure and an adjoined wired structure. The results of analytical calculations and numerical modeling show that the light emitted by a dipole placed on the top of the multilayered structure propagates within a narrow cone along the direction $\mathbf{n}$, where $\mathrm{Re}\phantom{\rule{0.2em}{0ex}}\ensuremath{\epsilon}(\ensuremath{\omega},\mathbf{n})=0$. Owing to impedance matching and negative refraction at the interface, a bright image with a maximum transverse size of approximately $50$ nm is focused in the wired structure at the wavelength $\ensuremath{\lambda}=670$ nm.

RRAM Devices with Plasma Treated HfO2 with Ru as Top Electrode for In-Memory Computing Hardware

Recently, many non-volatile memory devices such as resistive random-access memory (RRAM) have shown promise as candidates for analog in-memory computing applications related to inference and training in artificial intelligence. A RRAM cell has an MIM (metal insulator metal) structure that exhibits reversible resistive switching on application of positive or negative voltage. HfO2-based dielectrics with controlled distribution of defects or oxygen vacancies can potentially enable low power switching and multi-resistance levels. However, detailed studies of the power consumption, repeatability and retention during multi-level operation have not been undertaken previously. Transition metal oxide-based RRAM, using HfO2, executes change in resistance (switching behavior) via electrochemical migration of oxygen vacancies. Lack of enough oxygen vacancies in stoichiometric HfO2 limits the low power operation. Therefore, HfOx (with x < 2) has been studied for many RRAM devices (1). A uniform distribution of defects in HfO2 may help in switching but may not help in reducing the power. The distribution of these defects throughout the bulk of HfOx is, therefore, not well-understood. It was recently reported that high oxygen vacancy concentration close to top electrode reduces switching power (2).This work investigates the role of extra oxygen vacancies, introduced by plasma for a 6 nm thick HfO2 during deposition to reduce the power consumption. Initially TiN, which is a commonly used metal in CMOS technology, was used as the top electrode for treated HfO2 using a Si/PVD Ti/PVD TiN/HfO2/PVD TiN structure. A range of compliance currents (CC) from 1 nA to 500 nA were used to evaluate the switching characteristics. The TiN devices switch at and above a CC of 50 nA and were tested for sustainability for hundreds of cycles. In addition to oxygen vacancy rich treated-HfO2 near the top electrode, TaN and Ru electrodes were explored to enhance the switching behavior and power consumption. The role of both TaN and Ru as bottom metal was also evaluated. With Ru as top metal the Si/PVD Ti/PVD TiN/HfO2/Ru/PVD TiN structure, switched at 1 nA CC and at higher CC. Whereas when Ru was used as a bottom electrode, a Si/PVD Ti/PVD TiN/Ru/HfO2/ PVD TiN structure, devices were unable to switch below a CC of 50 mA. For TaN as top metal electrode, devices switched at and above 1 mA CC whereas with TaN as bottom metal the initial switching was at CC of 2 mA. It was concluded that use of Ru as a top metal significantly reduced the switching energy of the treated HfO2 RRAM device but was ineffective when used as a bottom metal. Potential mechanism for this observation will be discussed. References Chen, W. Lu, B. Long, Y. Li, D. Gilmer, G. Bersuker, S. Bhunia, and R. Jha, Semiconductor Science and Technology 30, 075002 (2015).Misra, P. Zhao, D. H. Triyoso, V. Kaushik, K. Tapily, R. D. Clark, S. Consiglio,2, T. Hakamata, C. S. Wajda, and G. J. Leusink, ECS J. Solid State Sci. Technol. 9, 05300, (2020).

Application of artificial neural networks to the identification of weak electrical regions in large area MIM structures

Large area metal-insulator-metal (MIM) structures are prone to exhibit weak electrical regions when they are subjected to severe stress conditions. Although the root cause of this problem is hard to identify, it has been attributed to non-uniform oxide thickness, variable dielectric permittivity, correlated defect generation, and fringe effects in capacitors. In this paper, we explore the application of artificial neural networks (ANNs) to the spatial localization of such weak regions. To this end, HfO2-based MIM structures were electrically stressed with the objective of generating a large number of breakdown spots. These spots are statistically distributed both in size and location over the device area. Two-input/two-output ANNs with different number of neurons and hidden layers were assessed with the purpose of identifying the best and simplest option for detecting where the most severe damage occurs. The obtained results are compatible with previous studies based on spatial statistics techniques. The method can be applied to other systems that exhibit multiple localized failure events.

Optical image edge detection by transmissive metal-dielectric-metal structures

The feasibility of an optical image edge detection based on metal-insulator-metal (MIM) resonance transmission structures is experimentally investigated. The structures are fabricated on a glass substrate and consist of thin aluminum layers separated by a quartz layer. The excitation of Fabry-Perot modes by an incident wave produces resonance line shapes in angular and wavelength transmission spectra. Resonance enhancement and suppression of beams using the MIM structures can be implemented for suppressing the illuminating beam and amplifying the field scattered by an object. By using the MIM structure under oblique incidence, we experimentally observe the efficient image edge detection for phase optical elements at a set of wavelengths. The obtained images of edges of the elements exhibit a directionality of image edge detection that depends on the direction of inhomogeneity gradient in the object plane, as suggested by the angular transmission spectra of the MIM structures. The results of the present work can find applications in optical information processing and optical filtering systems.

Compact multilayer thin-film color filters and direct integration on white-light-emitting diodes for color conversion.

We present highly efficient green, yellow, and red filters based on a metal-dielectric structure. The filters encompass only five layers of alternating zinc tin oxide and silver thin films that are grown on soda lime glass and white light-emitting diodes (LEDs) using direct current magnetron sputtering at room temperature. The designed filters provide efficient color filtering in the visible spectrum. High purity colored light is obtained by direct application of filters on LEDs as color converters. The presented method offers an easy way for realizing different colors by tuning the thicknesses of layers in the structure.

АНТЕНА НА ОСНОВІ ГІБРИДНОЇ МЕТАЛЕВО-ДІЕЛЕКТРИЧНОЇ СТРУКТУРИ

Purpose: Nowadays, in the millimeter frequency range, the dielectric waveguides of various modifications have certain advantages over the standard metal waveguides, primarily due to the possibility of creating functional units based on them. This is due to the relative simplicity and low cost of manufacturing the dielectric waveguides and functional units using them, the high degree of their integration with active elements, the use in their manufacture of different dielectrics and polymers with a wide range of material constants and a variety of mechanical properties (in particular, some materials have a significant flexibility). After making a series of physical experiments we have found the possibility of implementing the frequency selection and radiation into free space of electromagnetic waves by a hybrid metal-dielectric structure. Design/methodology/approach: The studied electrodynamic structure belongs to the class of hybrid metal-dielectric structures. It includes a modified inverted dielectric waveguide with a periodic sequence on the dielectric plate of fifteen dielectric rods with metallized coating on one of the faces placed outwards. The structure efficiency was estimated by the voltage standing-wave ratio (VSWR) values and power attenuation in the duct. The measurements were made with the reflectometer method. To estimate the degree of electromagnetic field concentration near the rod inhomogeneities in the near zone, the mobile probe method was used. The field structures were visualized with the method of isolines. Findings: The results of a series of experimental investigations showed the possibility of matching the structure with the external waveguides in the frequency range of 26.5-32.5 GHz with the voltage standing-wave ratio (VSWR) less than 1.8. The frequency dependence of attenuation is oscillatory with clearly expressed frequency ranges with small and large attenuation values. Moreover, the dependence is almost periodic, which is typical of periodic structures. The frequency response slope in the transition zones can be quite high and reach values of 41.26 dB/GHz. The degree of concentration of the electric field near the waveguide dielectric rod and the degree of excitation of the dielectric inhomogeneities was found by directly measured electric field strength in the near zone. Measurements of energy characteristics made under the short-circuit conditions for the main guide and in the mode of matched load of the main guide showed both the ability to control the polarization characteristics and the ability to change the appearance of the pattern and its orientation in space. Conclusions: It has been experimentally proven that a hybrid metal-dielectric structure, being a modified inverted dielectric waveguide with a periodic sequence on the dielectric plate of fifteen dielectric rods with metalized coating on one of the faces placed outwards, can be effectively integrated into a standard transmission line. It is found that this structure can be matched with the external circuits in a fairly wide frequency range. It is also found that in different frequency ranges this hybrid metal-dielectric structure shows the possibility of both efficient frequency selection and radiation in free space. Antenna measurements have shown the beam pattern shape controllability. Key words: inverted dielectric waveguide, periodic sequence, voltage standing-wave ratio (VSWR), attenuation, reflectometer method, mobile probe method, directivity pattern

Ultrafast Nonlinear Pulse Propagation Dynamics in Metal–Dielectric Periodic Photonic Architectures

Abstract1D metal–dielectric (MD) periodic structures take advantage of large refractive index contrast between metal and dielectrics to invoke extremely high nonlinear ultrafast responses of metal. These structures are also special due to their extremely high laser damage threshold. The Bragg‐like 1D MD structure (Ag/SiO2)4 enables strong optical field confinement with much enhanced nonlinear features as compared to simple metal or single (Ag/SiO2)1 structure. In the present work, the ultrafast nonlinear optical responses of the above structures are investigated via femtosecond broadband optical pump–probe technique. The enhanced nonlinear optical absorption is of reverse saturation of absorption nature, resulted due to free‐carrier absorption and excited‐state absorption processes. The spectral nonlinearities are closely related to the pump‐induced modification of the metal's dielectric functions, which are qualitatively visualized by transfer matrix and two‐temperature models. The ultrafast temporal evolution of nonlinear absorption clearly demonstrates enhanced optical nonlinearity, disentangled by the electron–electron and electron–phonon dynamic interactions at picosecond time scales. A phenomenological pulse propagation model is employed that incorporates the experimentally obtained nonlinear absorption coefficients and different nonlinear effects exhibited by the system. The findings of these new optical materials can possibly pave the way for promising applications in ultrafast photonics.

Using High-k VPP Modes in Grating-Coupled Graphene-Based Hyperbolic Metamaterial for Tunable Sensor Design

Volume plasmon polariton (VPP), a high- k mode that arises due to the coupling between two even modes of adjacent layers of an hyperbolic metamaterial (HMM) configuration, is very difficult to be excited by using prism coupling technique due to huge wave-vector mismatch. In this work, we present a graphene-based HMM structure integrated with metal grating to facilitate excitation of VPP modes. A graphene HMM is composed of multilayer graphene super-lattice similar to metal-dielectric super-lattice structure. We report the analytical formulation of the dispersion relation and numerical analysis of the characteristics of the excited VPP modes for the proposed structure in Terahertz frequency region. The best achieved imaging resolution (spatial) of our proposed structure is 15 nm when used as an infra-red imaging platform. As a sensing platform, a maximum sensitivity of 11,050 nm/RIU is achieved for this configuration. The tunability of the resonance wavelength with respect to the structural parameters of the device is also studied and confirmed. Such promising findings are expected to make the proposed structure with integrated excitation coupler a potential candidate for tunable sensor design for different nanophotonic applications, including imaging, and, biomedical and chemical sensing applications.